In terms of emission regulation, the future of the CPP is uncertain in the face of legal and political opposition. However, even in the absence of the CPP, low natural gas prices and environmental regulations will likely result in the retirement of coal-fired generation. There is likely to be a continued drive towards variable energy resources such as wind and solar which will continue to challenge grid operators. It will also be incumbent on regulators at both state and federal level to develop emission regulation with reliability concerns in mind.